still a bit hacky, but shows imgui windows that can be clicked etc

the integration of that at least, the menu is still a stub

idStr::(V)Format() is a static (v)printf-like function that returns
and idStr. Can be used like a better va(), or for
idStr mystr = idStr::Format( "number of items: %d", myarr.Num() );

I actually did this before the prototyping of a keybindings menu
in the imgui example code, so the prototype is actually based on this.
I'll merge the code from the prototype back once it's done.

The original binding menu uses #str_07183 between keys - this
should be " or ", but in the windows demo that entry is missing
in strings/english.lang

they're part of the regular list now. this will help with the actual
binding implementation I'll merge next

I first developed that as a prototype in
https://github.com/DanielGibson/dhewm3/blob/imgui/neo/libs/imgui/examples/example_sdl2_opengl2/main.cpp
there one can also find a commit history from writing that code, even
though not all commit messages are overly helpful :-p

Also fix MSVC build: For some reason Microsoft's sad excuse of a compiler
 only sets __cplusplus to a value from this millenium if the
/Zc:__cplusplus compiler option is set, but that's only supported from
VS2017 15.7 on. The alternative is to use _MSVC_LANG, which always holds
the version that __cplusplus *should* have...

You can pry X macros from my cold dead hands

it's nicely self-contained, I'll release it as a mini-library/addon
for Dear ImGui on https://github.com/DanielGibson/Snippets/

- write code uses fewer/shorter string literals
- code generated by WriteImGuiStyleToCode() has nicer alignment
- small improvements in some comments

Pause the game (with g_stopTime) when the settings menu is opened
while ingame, unpause it when it's closed.
If the menu is open while ingame and an ImGui window has focus,
the mouse cursor is shown. If the player clicks outside an ImGui window,
it gets unfocused and the cursor is hidden and the player can look
around. Pressing F10 (or whatever key is bound to "dhewm3Settings")
will give focus back to an open ImGui window, pressing it again then
will close the settings window, pressing it once again afterwards will
open the settings window again.

handleMouseGrab() (in sys/events.cpp) now checks if sys_imgui thinks
that a cursor should be shown (via D3::ImGuiHooks::ShouldShowCursor())
and if so, shows it and ungrabs the mouse. This, together with
D3::ImGuiHooks::NewFrame() checking ShouldShowCursor() to (unset)
ImGuiConfigFlags_NoMouseCursorChange, should prevent flickering cursor
problems that sometimes occurred when ImGui's SDL2 backend and dhewm3
disagreed on whether the cursor should be visible.

* Binding menu makes sure that the AllBindingsMenu always gets focus
  when opened
* Give binding-related popups slightly rounder edges
* Move Game Options tab behind Video and Audio Options
* Make warning overlays a bit less translucent

In the main menu the ImGui/SDL/System cursor was only drawn when it was
over an ImGui window, so only the Doom3 cursor is shown when outside
of ImGui windows.
The only problem with this is that the Doom3 cursor is only shown in
the parst of the window actually covered by the main menu, not the black
bars that are drawn on the left/right for widescreen-resolutions when
scaling the menu to 4:3 is enabled (which it is by default).
So now the ImGui cursor is also drawn when the cursor is on those
black bars (if any).

Also tweaked the windowtitle background colors a bit.

Not supported with SDL1.2 - but that's only still supported by dhewm3
because I'm too lazy to rip it out :-p

if set, the display resolution (r_mode) is not modified

- s_scaleDownAndClamp CVar so the clamping and scaling down of all
  sounds (that is done to prevent clipping) can be disabled
  (enabled by default)
- s_alOutputLimiter CVar to allow configuring ALC_SOFT_output_limiter
  which (if enabled) reduces the overall volume if it gets too loud,
  to avoid clipping (defaults to -1 = "let OpenAL decide")
- s_alHRTF to allow enabling or disabling HRTF, requires ALC_SOFT_HRTF
  (defaults to -1 = "let OpenAL decide")

Those CVars can be changed at runtime and are applied immediately
(in case of s_alHRTF and s_alOutputLimiter by resetting the OpenAL
 device, just like we do when a disconnect is detected)

in_allowAlwaysRunInSP allows using in_alwaysRun and in_toggleRun
in Single Player (it'll still drain your stamina!)

m_invertLook allows inverting mouse look, both for up/down and
left/right, if you're into that kind of thing

- convert to/from ISO8859-1 (Doom3's "High ASCII" encoding)
- count Unicode codepoints in UTF-8 string
- cut UTF-8 string off after N codepoints
- use the conversion function to replace iconv in sys/events.cpp

ImGui uses UTF-8 for strings, Doom3 uses ISO8859-1, so the playername
must be translated.
Also it seems like the playername should have at least 40 chars,
at least that's the limit imposed by the original Doom3 menu

and do it automatically when using SDL1.2, as it requires SDL2
(or SDL3 once we support it)

so it gets saved in the config

also added another Game Option and added separators to that menu

turns out ImGui also messes with the windows alpha chan, so, it
must render before the alpha chan is filled

for some reason <algorithm> dragged in <cstdio> which chocked on the
use_idStr_snPrintf #defines from Str.h
"fixed" by including <algorithm> first
also shut up some compiler warnings about signed/unsigned mismatch

using amalgamated miniz 3.0.2 from https://github.com/richgel999/miniz
and minizconf.h from Yamagi Quake II:
https://github.com/yquake2/yquake2/blob/master/src/common/unzip/miniz/minizconf.h

Upstream commit: "Disabled: nested tooltips or other non-child window
 within a BeginDisabled() block disable the disabled state. (dhewm#211, #7640)"

Should be in the next Dear ImGui release

the stb libs, miniz and minizip are now always optimized to speed up
performance, esp. level loading times, in debug builds.

So far the stb libs implementation were dragged into the source file
that uses them, now I created additional source files just for them so
those can be optimized while the engine source files using those libs
can remain unoptimized in debug builds.

ImGuiDir now is a proper enum, not just a typedef of int that happens
to have a similar name to the actual enum

Seems like calling ImGui::CalcTextSize() is only safe after
(or at the end of) NewFrame()

is this really all that's needed?!

incl. setting in SettingsMenu

With SDL 2.0.5 and newer this change is applied immediately,
2.0.0 to 2.0.4 need a vid_restart
(with SDL1.2 we don't support it at all)

"vid_restart partial" only changes the window size or its fullscreen
(or windowed) state, without recreating everything.
If that fails (or antialiasing settings have changed), it will fall back
to a full vid_restart (this behavior is different than original
 "vid_restart partial" that probably was implemented in Vanilla Doom3
 but not dhewm3)

This is used for Alt-Enter (which toggles between fullscreen and
windowed state) and when pressing the Apply button in the new Video Menu

Toggling with Alt-Enter relies on idRenderSystem::IsFullScreen() which
returns glConfig.isFullscreen

That can only work if GLimp_SetScreenParms() actually sets
glConfig.isFullscreen

Thanks j4reporting for reporting this! :)

it's queried from SDL so it should be up-to-date.
Using it in GLimp_SetScreenParms(), as it mostly did the same SDL calls
to get the current state for the partial vid_restart

…ions

Now the CVars are set immediately and "Apply" only does
`vid_restart partial`, while "Reset" resets the CVars to the values
that were set when opening the menu.
This also works the other way around: Changing a CVar (in the console
or other menu or r_fullscreen with Alt-Enter) is immediately reflected
in the menu.

Furthermore, "fullscreen desktop" now is its own setting (=> can be set
even if windowed mode is selected), to accommodate switchting between
windowed and fullscreen with Alt-Enter